Electrical precipitation apparatus



Dec. 7, 1937.

w DEUTSCH ELECTRICAL PRECIPITATION APPARATUS Filed Feb. 23, 1957 7 A I.5 E R f, 1 fi INVENTOR. WdDeuiscio, BYMM? M ATTR EYS.

Patented Dec. 7, 1937 PATENT OFFICE 2,101,168 ELECTRICAL PRECIPITATIONAPPARATUS Walther Dentsch, FrankIort-on-the-Main, Germany, assignor toInternational Precipitation Company, Los Angeles, Calif., a corporationoi California Application February 23, 1937, Serial No. 127,287 InGermany February 24, 1936 1 Claim.

This invention relates to the electrical treatment of fluids, in which afluid to be treatedeithera gas or a liquid-is passed through anelectrical field between opposirig electrode means. As examples of suchtreatments, there may be mentioned the electrical precipitation ofsuspended particles from gases, and the electrical de-emulsifying orseparation of liquid emulsions. The present invention is concernedparticularly with electrical fluid treating apparatus in which aunidirectional high potential field is maintained between the opposingelectrode means.

In such apparatus, it is frequently desirable to pass the fluidsuccessively through two electrical fields maintained between twoseparate sets or systems of oppositely charged electrode members, and inthese cases it is sometimes advantageous to apply potentials ofdifferent magnitudes between the opposing electrodes of the respectivesets or systems. For example, in the treatment of either gases orliquids, it may be desired to first subject the fluid to the action ofan electrical field at relatively low potential and then to the actionof a higher potential field. In other cases, different arrangements orspacings of the opposing electrodes, or different types of electrodes,may be employed in the successive fields, making it either necessary orpreferable to utilize potentials of different magnitudes.

The principal object of the invention is to provide a simple andadvantageous means of obtaining two unidirectional potentials ofdifierent magnitudes and applying these potentials to the respectiveelectrode systems in an apparatus such as above described.

A further object is to provide for obtaining the two differentunidirectional potentials from a common source of alternating electriccurrent, and with the employment of a single mechanical rectifyingapparatus of simple design and construction.

The rectifier employed according to this invention is a 'polyphasemechanical rectifier, which may be of the general type described inGerman as the respective electrodes of an electrode system) whereby,successive pairs of phases are successively connected in series to theterminals of the load. The operation is such that one terminal of theload is substantially continuously connected to a point of highestpositive potential of the polyphase source and the other terminal issubstantially continuously connected to a point of highest negativepotential of said source, so that the effective unidirectional potentialsupplied to the load is approximately twice the efiective potential ofthe individual phases. According to the present invention, a separateunidirectional potential is also supplied to another load (in this casethe respective electrodes of a separate electrode system) by connectingone terminal of. this other load to one of the rotating contact membersof the rectifier, and connecting the other terminal of this load to thestar-point or common connection of the several phase windings of thealternating current source, so that the rectified voltages of theindividual phases are successively connected to this other load. Thus,the potential applied to the last mentioned load is approximately'halfthe potential applied to the first mentioned load. It will be understoodthat rectification may be obtained ina similar manner by connecting theloads to fixed contact means and connecting the several phases of thepolyphase source to rotating contact means, but the arrangement firstdescribed is ordinarily preferred, since it minimizes the number ofbrush contacts required to maintain connection to the rotating contactmeans.

The following specific description will serve to illustrate theapplication of this invention to one particular type of apparatus forelectrical precipitation of suspended material from gas, but it will beunderstood that the invention may be employed in a like or comparablemanner in connection with any apparatus in which a fluid, either gas orliquid, is passed successively between two separate electrode systems,and in which it is desired to supply unidirectional potentials ofdifierent magnitudes to the opposing electrodes of the respectivesystems.

According to one method which has long been known for the electricalseparation of suspended solid or liquid particles from gases, the gas isfirst passed through a unidirectional electrical field in whichionization is caused to occur, for the purpose of electrically chargingthe suspended particles, and is then passed through a separateunidirectional field in which substantially no ionization is produced,for the purpose of precipitating the charged particles. In apparatus ofthis type, 5

some difliculty has been encountered in obtaining suillcient ionizationin the first or charging field to efiectively charge the suspendedparticles, without causing an objectionably large proportion of thesuspended particles to be actually precipitated in this field instead ofin the second or precipitating held in which, according to this method,the actual separation may be more advantageously carried out.

For the above reason, it is advantageous in some cases to pass the gasthrough the charging held at a velocity severaljimes as great as thevelocity at which it is passed through the precipitating field. This maybe accomplished adtactmembers 2|,22 andiispecedlzflapartin' position forefiective spark contact with mental;- ing contact is and connededrespectively totheextremitiesoithesevm'alphase vantageously by placingthe electrodes relatively I, l1 and III. The inner ends of the severalclose together in the charging field, to provide a phases are cotogether at a common point gas passage space therebetween of relativelysmall 2!, commonly referred to as the star-point.

cross-sectional area, and placing the electrodes It will be understoodthat the rotating contact relatively farther apart in the precipitatingfield, assembly of the rectifier may be mounted in the to provide a gaspassage space therebetween usual manner upon the shaft of a synchronouswhose cross-sectional area is several times that motor for rotation inthe proper direction, for exof the charging field. For example, thecharging ample as shown by the arrow in Fig. 1, and that electrodesystem may comprise a. discharging suitable insulating means areprovided for elecelectrode formed as a wire of sufliciently smalltrically insulating the segments 12 and I2 and diameter to provideeiiective corona discharge or conductor ll hum ts l3 and i3and-conionization, disposed axially within a. substantially ductor l6.Owing to the fact that the device is cylindrical tube or pipe whichconstitutes the opshown as provided with two contact to posingnondischarging electrode or extended for each polarity of the rectifiedpotential, the

surface, while the precipitating electrode system rotating is operatedat one-half synmay comprise two concentric cylindrical electrodemembers, both of suiiiciently extended surface to substantially preventcorona discharge therefrom, and spaced from one another by a distancesomewhat greater than the spacing of the two electrodes of the chargingfield, so as to provide the desired increase in cross-sectional area. ofthe gas passage space therebetween.

mth such an arrangement, it becomes desirchronous speed, as by means ofa four-pole synchronous motor, soihat 180 rotation thereof correspondsto 360 electrical degrees. It will be understood, however, that only onerotating contact segment for each polarity may be provided, in whichcase thetwo ts would he located 180" apart in space, and the rotatingassembly would be operated at synchronous speed.

The elezarical precipitator is shown as comable to apply a higherpotential to the electrodes prising a. charging zone or field 25 and aprecipiof the precipitating electrode system than to the tating zone orfield 26. The electrode system in electrodes of the charging electrodesystem, and the charging field comprises a non the arrangement accordingto the present invenp pe e de Ti d a di charge electrode memtion may beemployed advantageously for this er 2 such as a wire or thelikc,extending axialpurpose, Y t 51y within said pipe and insulatedtherei'rmn. The

The accompanying drawing illustrates the inelectrode system of the zonecomvention as applied to an apparatus of this type prises anon-discharging cylindrical electrode and reigning thereto: 9 member 290f sufliciently extended surface, and

Fig. 1 is a diagrammatic representation of an preferably rounded at itsends 115 811m, P electrical precipitation apparatus of the type ventcorona discharge therefrom, and a. pipe or above described and anassociated electric circuit y fi fi electrode m r fl fl fl arrangementaccording to this invention; surrounding and insulated from theelectrode 2!.

Fig. 2 is a diagram of the poiyphase potential E r es an 3! ar l ricallygrounded as supplied by the alternating current source; indicated at 3!.The other electrode 28 of the Fig. 3 is a diagram representing thepositive p ifi at ng el de System is connected and negative potentialsapplied to the respective through the above mentioned conductor ll tothe rotating contact members of the rectifier; and high lifinsion conctnts l3 and 13', while Fig. 4 is a diagram of the rectified potentialsthe other electrode 28 of the charging electrode supplied to therespective electrode systems, it system is connected by conductor 32 tothe above being understood that the relationships shown in mentioned -Pt m ctmncction 01' Figs. 3 and 4 are somewhat idealized for purposes hehre s m I 11 and 331 0f the inc of illustration. current source.

Referring to Fig. l, the secondary phase wind- The be filmed Elli/BISthe zone ings of a high potential three-phase transformer at 33 and isconducted from this zone by a due or are shown at I, II and III. pipeconnection 34 to the zone, Th

The rectifier comprises a rotating assembly incleaned gas is tom theopen upper dicated tieally at ll provided with t end of the tubularelectrode 3!, and suitable diametrically opposed contact segments iland12' n h as a pp r re provided below and another pair of diametricallyopposed contact the p c pi a ng me r meeiving and collectsegments 13 and13' disposed circumferentially ns the midway between the contact segmmtsl2 and l 2. Referring to the potentials of e everal The contact segments12 and i2 are electrically phase windings I, II and HI (and consequentlyconnected together as at I4 and are shown as the Potentialsmaintaineflfitheflmdmnm grounded at 15. This connection may be made 22and 23) are-represented at E1, E1 and E3, reeither through the shaft ofthe rotating assembly spectiveb. This flame represents telyorbymeansofabrushorothersuitablecontact onefullcycleof cm'rentlnwhich'llelectrical degrees are plot-ted horizontally, while the ordinates of therespective curves with respect to the zero axis --0 represent thedifference in potential between the respective fixed'contacts '2l, 22and 23 and the star-point 24.

In the operation of the rectifier, the efiective contacts between thefixed and rotating contact elements are made and broken at timescorresponding substantially to the points of intersection of therespective curves in Fig. 2. For purposes of illustration, it may beassumed that the high tension electrodes 28 and 29 of the respectiveelectrode systems are to be maintained at positive potentials withrespect to the grounded electrodes 21 and 30, respectively. In thiscase, the rectifier is so operated that one or the other of the hightension rotating contact segments l3 or it is substantially at all timesin contact with a fixed contact member which is at the greatest positivepotential, while one of the grounded rotating contact segments I2 or I2is substantially at all times in contact with a fixed contact memberwhich is at the greatest negative potential, so that, at any instant,the combined potentials of the two phases corresponding to the two fixedcontact members so contacted are impressed in series upon the respectiveelectrodes 29 and 30 of the precipitating electrode system, while thepotential of the individual phase corresponding to the fixed contactwhich is at that time contacted by one of the grounded rotating contactsegments I2 and I2 is impressed upon the electrodes 21 and 28 of thecharging electrode system, due to thepremanent connection of hightension electrode 28 to the star-point 24 of neutral or intermediatepotential. l

Referring to Fig. 3, the positive potential supplied to the set ofrotating contact segments l3 and I3 is represented by the curve E13,which corresponds in position to the positive peak portions of theseveral phase potential curves E1, E2 and E: of Fig. 2. Similarly; thenegative potential supplied to the high tension set of rotating contactsegments l2 and I2 is represented by the curve A E12, which correspondsto the negative peak portions of the several phase potential curves E1,E2 and E3. Thus, the vertical distance between these two curves, asindicated by the line 38, represents the unidirectional potentialsupplied to the precipitating electrodes 29 and 30, while the verticaldistance between curve E12 and the zero axis 0-0, as indicated by theline 39, represents the.

unidirectional potential supplied to the charging electrodes 21 and 28.

The fluctuating unidirectional potentials of the respective electrodesystems are more clearly shown in Fig. 4, in which curve'E representsthe potential of the electrode 29 with respect to the grounded electrode30 of the precipitating zone, while Ec represents the potential of theelectrode 28 with respect to the grounded electrode 21 of the chargingzone, the ground potential line being shown at 0'-0. It will be seenthat the curve Ep has sixpeaks per cycle of the alternating current,while the curve E0 has three peaks per cycle of the alternating current,and that the eflective potential in the precipitating zone isapproximately twice the effective potential in the charging zone.

It will be understood that the spacing between electrodes 27 and 28 inthe charging zone is such as to provide the desired corona dischargefrom electrode 28, without producing disruptive discharge or arcing,while the spacing between electrodes 29 and 30 is such as to provide ahigh electrostatic field therebetween without disruptive discharge. Dueto the difference in the potentials in these two fields, the electrodespacing in the precipitating field may be in the neighborhood of twicethat in the charging field, thus obtaining the above mentioned advantageof a relatively high velocity in the charging field as compared with theprecipitating field.

I claim:

An apparatus for electrical treatment of fluids comprising two separateelectrode systems each comprising two opposing electrode members spacedfrom one another to accommodate flow of gas therebetween; a polyphasetransformer with Y-connected secondary phasewindings having a commonpoint connected to one end of each winding; means electricallyconnecting one electrode member of one of said electrode systems to saidcommon point; and synchronously operated mechanical rectifying meansassociated with the other terminals of said windings, and with the otherelectrode member of said one system, and also with the two electrodes ofthe other electrode system, said rectifying means being operable tosuccessively connect the several phases individually to said otherelectrode member of said one system and to successively connectdifi'erent successive pairs of phases in series between the twoelectrode members of said other system.

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